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The reconstruction of high-pt photons with the electromagnetic calorimeter of the ALICE experiment at the LHC
In two years, the frontier of relativistic heavy ion physics will move to the Large Hadron Collider (LHC), which will explore matter with energy densities greater than 10 times that at the Relativistic Heavy Ion Collider (RHIC), providing an opportunity to test predictions of Quantum Chromodynamics...
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| Format: | Thesis |
| Language: | English English |
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Department of Physics
2025
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| _version_ | 1867613688256528385 |
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| access_status_str | Open Access |
| author | Gray, Heather M |
| author2 | Cleymans, Jean |
| author_browse | Cleymans, Jean Gray, Heather M |
| author_facet | Cleymans, Jean Gray, Heather M |
| author_sort | Gray, Heather M |
| collection | Thesis |
| description | In two years, the frontier of relativistic heavy ion physics will move to the Large Hadron Collider (LHC), which will explore matter with energy densities greater than 10 times that at the Relativistic Heavy Ion Collider (RHIC), providing an opportunity to test predictions of Quantum Chromodynamics (QCD). At the LHC, the cross-sections for high momentum processes are expected to be sufficiently large for jet physics to play an important role. Some first hints of this exciting physics have already been reported at RHIC energies, namely observation of jet quenching, as indicated by the suppression of the yield of high Pt hadrons and the suppressed yield of back-to-back correlated hadrons from jets, in central Au+Au collisions. However, careful jet and jet quenching analyses require calibration with the parton energy prior to its passage though the nuclear matter. This can only be obtained via analysis of 1 -jet processes because photons, once produced, are essentially unaffected by a colour-charged medium, and pass through the medium retaining their original energy. The experimental challenges include identifying photons within the high multiplicity heavy-ion environment and reducing the background from the photonic decays of neutral pions. This thesis details algorithms developed for photon reconstruction in the heavy-ion envi-ronment for the electromagnetic calorimeter (EMCal) of the ALI experiment. Shower shape analysis was used to optimise cuts to discriminate between the direct photon signal and the background from the photonic decays of neutral pions. Photon energy resolution of approxi-mately 5% at 10 GeV and 3% at 30 GeV was obtained in simulations. An enhancement in the ratio by a factor of 50 relative to theoretical predictions at 20 GeV was obtained using the techniques of shower shape analysis |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/42026 |
| institution | University of Cape Town (South Africa) |
| language | English eng |
| last_indexed | 2026-06-10T12:40:07.459Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Department of Physics |
| publisherStr | Department of Physics |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/42026 The reconstruction of high-pt photons with the electromagnetic calorimeter of the ALICE experiment at the LHC Gray, Heather M Cleymans, Jean Odyniec, Grazyna Quantum Chromodynamics In two years, the frontier of relativistic heavy ion physics will move to the Large Hadron Collider (LHC), which will explore matter with energy densities greater than 10 times that at the Relativistic Heavy Ion Collider (RHIC), providing an opportunity to test predictions of Quantum Chromodynamics (QCD). At the LHC, the cross-sections for high momentum processes are expected to be sufficiently large for jet physics to play an important role. Some first hints of this exciting physics have already been reported at RHIC energies, namely observation of jet quenching, as indicated by the suppression of the yield of high Pt hadrons and the suppressed yield of back-to-back correlated hadrons from jets, in central Au+Au collisions. However, careful jet and jet quenching analyses require calibration with the parton energy prior to its passage though the nuclear matter. This can only be obtained via analysis of 1 -jet processes because photons, once produced, are essentially unaffected by a colour-charged medium, and pass through the medium retaining their original energy. The experimental challenges include identifying photons within the high multiplicity heavy-ion environment and reducing the background from the photonic decays of neutral pions. This thesis details algorithms developed for photon reconstruction in the heavy-ion envi-ronment for the electromagnetic calorimeter (EMCal) of the ALI experiment. Shower shape analysis was used to optimise cuts to discriminate between the direct photon signal and the background from the photonic decays of neutral pions. Photon energy resolution of approxi-mately 5% at 10 GeV and 3% at 30 GeV was obtained in simulations. An enhancement in the ratio by a factor of 50 relative to theoretical predictions at 20 GeV was obtained using the techniques of shower shape analysis 2025-10-23T10:37:45Z 2025-10-23T10:37:45Z 2005 2025-10-23T10:34:48Z Thesis / Dissertation Masters MSc http://hdl.handle.net/11427/42026 en eng application/pdf Department of Physics Faculty of Science University of Cape Town |
| spellingShingle | Quantum Chromodynamics Gray, Heather M The reconstruction of high-pt photons with the electromagnetic calorimeter of the ALICE experiment at the LHC |
| thesis_degree_str | Master's |
| title | The reconstruction of high-pt photons with the electromagnetic calorimeter of the ALICE experiment at the LHC |
| title_full | The reconstruction of high-pt photons with the electromagnetic calorimeter of the ALICE experiment at the LHC |
| title_fullStr | The reconstruction of high-pt photons with the electromagnetic calorimeter of the ALICE experiment at the LHC |
| title_full_unstemmed | The reconstruction of high-pt photons with the electromagnetic calorimeter of the ALICE experiment at the LHC |
| title_short | The reconstruction of high-pt photons with the electromagnetic calorimeter of the ALICE experiment at the LHC |
| title_sort | reconstruction of high pt photons with the electromagnetic calorimeter of the alice experiment at the lhc |
| topic | Quantum Chromodynamics |
| url | http://hdl.handle.net/11427/42026 |
| work_keys_str_mv | AT grayheatherm thereconstructionofhighptphotonswiththeelectromagneticcalorimeterofthealiceexperimentatthelhc AT grayheatherm reconstructionofhighptphotonswiththeelectromagneticcalorimeterofthealiceexperimentatthelhc |